Is "Quarter",QUARTER([Date]) same as "Quarter",FORMAT([Date],"Q")?
I realized that the "Quarter" column can also be created using <"Quarter",QUARTER([Date]),>. May I ask if it is the same as <"Quarter",FORMAT([Date],"Q"),>? Will it make any difference later on when create visuals/measures etc?
it is not, QUARTER function on its own will give you the quarter as in number - 1,2,3,4 so Power BI will recognize them as int rather than a string, because you want to be able to filter by the Quarter. When used inside the FORMAT function the integer becomes a string because it concatenates Q with the quarter number